REPOET ON THE OSTRACODA. ' 135 



behind, height equal to half the length ; anterior extremity rounded and divided below 

 the middle into four or five small teeth ; posterior oljliquely truncated, irregularly notched 

 and produced above the middle into a wide prominent beak, dorsal and ventral margins 

 nearly straight ; seen from above, the outline is broadly ovate, with pointed extremities ; 

 end-view subhexagonal, excavated between the angles. The surface of each valve is 

 divided into several large angular hollows by sharply-cut flcxuous ribs, the two principal 

 of which run from a point near the anterior border to the posterior extremity of the 

 valve, diverging at an acute angle, and enclosing a large portion of the area of the valve 

 in one large cavity, the surrounding portion being cut up info irregular hollows by 

 shorter separating ribs. Length, l-62d of an inch ("40 mm.). 



One specimen of this remarkably sculptured species was found in the dredging from 

 off East Moncoeur Island, Bass' Strait, in a depth of 38 to 40 fathoms. Though at first 

 perfect, the two valves, unfortunately, became separated in examination, so that I have 

 not been able to figure the complete shell. 



[PL XXXII. fig. 4, a-c. a Left valve seen from side, h the same from above, c from 

 front. Magnified 60 diameters.] 



Cytheropteron, G. 0. Sars (1865)., 



Valves mostly subrhomboidal, tumid, unequal, and difi"erent in shape, the right valve- 

 more or less overlapping the left on the dorsal margin ; surface of the shell variously 

 sculptured, punctate, papillose, reticulated, or transversely rugose, ventral surface pro- 

 duced laterally into a prominent rounded or spinous ala ; posterior margin produced into 

 a more or less distinct but obtuse beak ; hinge formed by two small terminal teeth on 

 the right, and by a minutely-crenated median bar on the left, valve. Muscle-spots 

 usually four, linear-oblong, arranged in an obhquely transverse row just above the 

 middle of the ventral margin. Anterior antennae shortly setiferous, and comjjosed of 

 five joints ; the penultimate joint elongated, and bearing on the middle of the anterior 

 margin two hairs ; posterior antennae distinctly five-jointed, flagellum long. Mandibles 

 of moderate size ; palp three-jointed, branchial appendage bearing two very small set^ ; 

 maxUlae as in the preceding genus. Feet long and slender, with slender terminal claws. 

 Abdomen ending in a long, narrow process ; postabdominal lobes bearing three short 

 hairs. Copulative organs of the male armed behind with three spiniform processes, 

 one of which is trifurcate. Eyes wanting. 



This is a cosmopolitan genus, containing a considerable number of species, of which 

 the best known are Cytheropteron latissimum (Norman), and Cytheropteron nodosum, 

 Brady. Both of these are northern species rangmg across the Atlantic from Canada to 

 Norway, and extending, in the case of the first named, as far northward as Baflin's Bay 

 and 'Spitzbergen, and occurring also very plentifully in the Post-Tertiary formations of 



